diff --git a/readme.md b/readme.md
index 9120be6..ca03ce9 100644
--- a/readme.md
+++ b/readme.md
@@ -1,6 +1,11 @@
 # Key-Value Store by [@adammbalogh](http://twitter.com/adammbalogh)
 
 [![Build Status](https://img.shields.io/travis/adammbalogh/key-value-store/master.svg?style=flat)](https://travis-ci.org/adammbalogh/key-value-store)
+[![Quality Score](https://img.shields.io/scrutinizer/g/adammbalogh/key-value-store.svg?style=flat)](https://scrutinizer-ci.com/g/adammbalogh/key-value-store)
 [![Software License](https://img.shields.io/badge/license-MIT-blue.svg?style=flat)](LICENSE)
 
 [![SensioLabsInsight](https://insight.sensiolabs.com/projects/f1ddb443-d2a1-499a-926a-060cdecd4100/small.png)](https://insight.sensiolabs.com/projects/f1ddb443-d2a1-499a-926a-060cdecd4100)
+
+# Support
+
+[![Support with Gittip](http://img.shields.io/gittip/adammbalogh.svg?style=flat)](https://www.gittip.com/adammbalogh/)
diff --git a/src/Adapter/AbstractAdapter.php b/src/Adapter/AbstractAdapter.php
new file mode 100644
index 0000000..abf85b2
--- /dev/null
+++ b/src/Adapter/AbstractAdapter.php
@@ -0,0 +1,14 @@
+<?php namespace AdammBalogh\KeyValueStore\Adapter;
+
+use AdammBalogh\KeyValueStore\Contract\AdapterInterface;
+
+abstract class AbstractAdapter implements AdapterInterface
+{
+    /**
+     * @return $this
+     */
+    public function getAdapter()
+    {
+        return $this;
+    }
+}
diff --git a/src/Adapter/NullAdapter.php b/src/Adapter/NullAdapter.php
new file mode 100644
index 0000000..39fe2ca
--- /dev/null
+++ b/src/Adapter/NullAdapter.php
@@ -0,0 +1,6 @@
+<?php namespace AdammBalogh\KeyValueStore\Adapter;
+
+class NullAdapter extends AbstractAdapter
+{
+    use NullAdapter\ClientTrait, NullAdapter\KeyTrait, NullAdapter\StringTrait;
+}
diff --git a/src/Adapter/NullAdapter/ClientTrait.php b/src/Adapter/NullAdapter/ClientTrait.php
new file mode 100644
index 0000000..5a284d5
--- /dev/null
+++ b/src/Adapter/NullAdapter/ClientTrait.php
@@ -0,0 +1,17 @@
+<?php namespace AdammBalogh\KeyValueStore\Adapter\NullAdapter;
+
+trait ClientTrait
+{
+    /**
+     * @var null
+     */
+    protected $client;
+
+    /**
+     * @return null
+     */
+    public function getClient()
+    {
+        return $this->client;
+    }
+}
diff --git a/src/Adapter/NullAdapter/KeyTrait.php b/src/Adapter/NullAdapter/KeyTrait.php
new file mode 100644
index 0000000..35a3ce5
--- /dev/null
+++ b/src/Adapter/NullAdapter/KeyTrait.php
@@ -0,0 +1,104 @@
+<?php namespace AdammBalogh\KeyValueStore\Adapter\NullAdapter;
+
+use AdammBalogh\KeyValueStore\Exception\KeyNotFoundException;
+
+/**
+ * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+ */
+trait KeyTrait
+{
+    use ClientTrait;
+
+    /**
+     * @param string $key
+     *
+     * @return bool True if the deletion was successful, false if it was unsuccessful.
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     */
+    public function delete($key)
+    {
+        throw new KeyNotFoundException();
+    }
+
+    /**
+     * @param string $key
+     * @param int $seconds
+     *
+     * @return bool True if the timeout was set, false if the timeout could not be set.
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     */
+    public function expire($key, $seconds)
+    {
+        throw new KeyNotFoundException();
+    }
+
+    /**
+     * @param string $key
+     * @param int $timestamp
+     *
+     * @return bool True if the timeout was set, false if the timeout could not be set.
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     */
+    public function expireAt($key, $timestamp)
+    {
+        throw new KeyNotFoundException();
+    }
+
+    /**
+     * @return array
+     */
+    public function getKeys()
+    {
+        return [];
+    }
+
+    /**
+     * Returns the remaining time to live of a key that has a timeout.
+     *
+     * @param string $key
+     *
+     * @return int Ttl in seconds
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException If the key exists but has no associated expire.
+     */
+    public function getTtl($key)
+    {
+        throw new KeyNotFoundException();
+    }
+
+    /**
+     * @param string $key
+     *
+     * @return bool True if the key does exist, false if the key does not exist.
+     *
+     * @throws \InvalidArgumentException
+     */
+    public function has($key)
+    {
+        return false;
+    }
+
+    /**
+     * Remove the existing timeout on key, turning the key from volatile (a key with an expire set)
+     * to persistent (a key that will never expire as no timeout is associated).
+     *
+     * @param string $key
+     *
+     * @return bool True if the persist was success, false if the persis was unsuccessful.
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     */
+    public function persist($key)
+    {
+        throw new KeyNotFoundException();
+    }
+}
diff --git a/src/Adapter/NullAdapter/StringTrait.php b/src/Adapter/NullAdapter/StringTrait.php
new file mode 100644
index 0000000..4c56c59
--- /dev/null
+++ b/src/Adapter/NullAdapter/StringTrait.php
@@ -0,0 +1,141 @@
+<?php namespace AdammBalogh\KeyValueStore\Adapter\NullAdapter;
+
+use AdammBalogh\KeyValueStore\Exception\InternalException;
+use AdammBalogh\KeyValueStore\Exception\KeyAlreadyExistsException;
+use AdammBalogh\KeyValueStore\Exception\KeyNotFoundException;
+
+/**
+ * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+ */
+trait StringTrait
+{
+    use ClientTrait;
+
+    /**
+     * @param string $key
+     * @param string $value
+     *
+     * @return int The length of the string after the append operation.
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
+    public function append($key, $value)
+    {
+        throw new KeyNotFoundException();
+    }
+
+    /**
+     * @param string $key
+     *
+     * @return int The value of key after the decrement
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
+    public function decrement($key)
+    {
+        throw new KeyNotFoundException();
+    }
+
+    /**
+     * @param string $key
+     * @param int $decrement
+     *
+     * @return int The value of key after the decrement
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
+    public function decrementBy($key, $decrement)
+    {
+        throw new KeyNotFoundException();
+    }
+
+    /**
+     * @param string $key
+     *
+     * @return string The value of the key
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
+    public function get($key)
+    {
+        throw new KeyNotFoundException();
+    }
+
+    /**
+     * @param string $key
+     *
+     * @return int
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
+    public function getValueLength($key)
+    {
+        throw new KeyNotFoundException();
+    }
+
+    /**
+     * @param string $key
+     *
+     * @return int The value of key after the increment
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
+    public function increment($key)
+    {
+        throw new KeyNotFoundException();
+    }
+
+    /**
+     * @param string $key
+     * @param int $increment
+     *
+     * @return int The value of key after the increment
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
+    public function incrementBy($key, $increment)
+    {
+        throw new KeyNotFoundException();
+    }
+
+    /**
+     * @param string $key
+     * @param string $value
+     *
+     * @return bool True if the set was successful, false if it was unsuccessful
+     *
+     * @throws \InvalidArgumentException
+     */
+    public function set($key, $value)
+    {
+        return false;
+    }
+
+    /**
+     * @param string $key
+     * @param string $value
+     *
+     * @return bool True if the set was successful, false if it was unsuccessful
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyAlreadyExistsException
+     */
+    public function setIfNotExists($key, $value)
+    {
+        return false;
+    }
+}
diff --git a/src/Contract/KeyInterface.php b/src/Contract/KeyInterface.php
index 7895b46..d00f136 100644
--- a/src/Contract/KeyInterface.php
+++ b/src/Contract/KeyInterface.php
@@ -1,18 +1,79 @@
 <?php namespace AdammBalogh\KeyValueStore\Contract;
 
+use AdammBalogh\KeyValueStore\Exception\InternalException;
+use AdammBalogh\KeyValueStore\Exception\KeyNotFoundException;
+
 interface KeyInterface
 {
+    /**
+     * @param string $key
+     *
+     * @return bool True if the deletion was successful, false if it was unsuccessful.
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     */
     public function delete($key);
 
+    /**
+     * @param string $key
+     * @param int $seconds
+     *
+     * @return bool True if the timeout was set, false if the timeout could not be set.
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     */
     public function expire($key, $seconds);
 
+    /**
+     * @param string $key
+     * @param int $timestamp
+     *
+     * @return bool True if the timeout was set, false if the timeout could not be set.
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     */
     public function expireAt($key, $timestamp);
 
+    /**
+     * @return array
+     */
     public function getKeys();
 
+    /**
+     * Returns the remaining time to live of a key that has a timeout.
+     *
+     * @param string $key
+     *
+     * @return int Ttl in seconds
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException If the key exists but has no associated expire.
+     */
     public function getTtl($key);
 
+    /**
+     * @param string $key
+     *
+     * @return bool True if the key does exist, false if the key does not exist.
+     *
+     * @throws \InvalidArgumentException
+     */
     public function has($key);
 
+    /**
+     * Remove the existing timeout on key, turning the key from volatile (a key with an expire set)
+     * to persistent (a key that will never expire as no timeout is associated).
+     *
+     * @param string $key
+     *
+     * @return bool True if the persist was success, false if the persis was unsuccessful.
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     */
     public function persist($key);
 }
diff --git a/src/Contract/StringInterface.php b/src/Contract/StringInterface.php
index b22bc3f..d60a6cf 100644
--- a/src/Contract/StringInterface.php
+++ b/src/Contract/StringInterface.php
@@ -1,22 +1,109 @@
 <?php namespace AdammBalogh\KeyValueStore\Contract;
 
+use AdammBalogh\KeyValueStore\Exception\InternalException;
+use AdammBalogh\KeyValueStore\Exception\KeyAlreadyExistsException;
+use AdammBalogh\KeyValueStore\Exception\KeyNotFoundException;
+
 interface StringInterface
 {
+    /**
+     * @param string $key
+     * @param string $value
+     *
+     * @return int The length of the string after the append operation.
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
     public function append($key, $value);
 
-    public function decr($key);
+    /**
+     * @param string $key
+     *
+     * @return int The value of key after the decrement
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
+    public function decrement($key);
 
-    public function decrBy($key, $decrement);
+    /**
+     * @param string $key
+     * @param int $decrement
+     *
+     * @return int The value of key after the decrement
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
+    public function decrementBy($key, $decrement);
 
+    /**
+     * @param string $key
+     *
+     * @return string The value of the key
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
     public function get($key);
 
+    /**
+     * @param string $key
+     *
+     * @return int
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
     public function getValueLength($key);
 
-    public function incr($key);
+    /**
+     * @param string $key
+     *
+     * @return int The value of key after the increment
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
+    public function increment($key);
 
-    public function incrBy($key, $increment);
+    /**
+     * @param string $key
+     * @param int $increment
+     *
+     * @return int The value of key after the increment
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
+    public function incrementBy($key, $increment);
 
+    /**
+     * @param string $key
+     * @param string $value
+     *
+     * @return bool True if the set was successful, false if it was unsuccessful
+     *
+     * @throws \InvalidArgumentException
+     */
     public function set($key, $value);
 
+    /**
+     * @param string $key
+     * @param string $value
+     *
+     * @return bool True if the set was successful, false if it was unsuccessful
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyAlreadyExistsException
+     */
     public function setIfNotExists($key, $value);
 }
diff --git a/src/Exception/InternalException.php b/src/Exception/InternalException.php
new file mode 100644
index 0000000..275a8d4
--- /dev/null
+++ b/src/Exception/InternalException.php
@@ -0,0 +1,5 @@
+<?php namespace AdammBalogh\KeyValueStore\Exception;
+
+class InternalException extends \Exception
+{
+}
diff --git a/src/Exception/KeyAlreadyExistsException.php b/src/Exception/KeyAlreadyExistsException.php
new file mode 100644
index 0000000..493c744
--- /dev/null
+++ b/src/Exception/KeyAlreadyExistsException.php
@@ -0,0 +1,5 @@
+<?php namespace AdammBalogh\KeyValueStore\Exception;
+
+class KeyAlreadyExistsException extends \Exception
+{
+}
diff --git a/src/Implementation/AdapterTrait.php b/src/Implementation/AdapterTrait.php
index 3ced405..cf6fc13 100644
--- a/src/Implementation/AdapterTrait.php
+++ b/src/Implementation/AdapterTrait.php
@@ -4,15 +4,13 @@
 
 trait AdapterTrait
 {
-    use KeyTrait, StringTrait;
-
     /**
      * @var AdapterInterface
      */
     protected $adapter;
 
     /**
-     * {@inheritdoc}
+     * @return AdapterInterface
      */
     public function getAdapter()
     {
diff --git a/src/Implementation/KeyTrait.php b/src/Implementation/KeyTrait.php
index ad32d55..dc3ad65 100644
--- a/src/Implementation/KeyTrait.php
+++ b/src/Implementation/KeyTrait.php
@@ -1,37 +1,100 @@
 <?php namespace AdammBalogh\KeyValueStore\Implementation;
 
+use AdammBalogh\KeyValueStore\Exception\InternalException;
+use AdammBalogh\KeyValueStore\Exception\KeyNotFoundException;
+
 trait KeyTrait
 {
+    use AdapterTrait;
+
+    /**
+     * @param string $key
+     *
+     * @return bool True if the deletion was successful, false if it was unsuccessful.
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     */
     public function delete($key)
     {
         $this->adapter->delete($key);
     }
 
+    /**
+     * @param string $key
+     * @param int $seconds
+     *
+     * @return bool True if the timeout was set, false if the timeout could not be set.
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     */
     public function expire($key, $seconds)
     {
         $this->adapter->expire($key, $seconds);
     }
 
+    /**
+     * @param string $key
+     * @param int $timestamp
+     *
+     * @return bool True if the timeout was set, false if the timeout could not be set.
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     */
     public function expireAt($key, $timestamp)
     {
         $this->adapter->expireAt($key, $timestamp);
     }
 
+    /**
+     * @return array
+     */
     public function getKeys()
     {
         $this->adapter->getKeys();
     }
 
+    /**
+     * Returns the remaining time to live of a key that has a timeout.
+     *
+     * @param string $key
+     *
+     * @return int Ttl in seconds
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException If the key exists but has no associated expire.
+     */
     public function getTtl($key)
     {
         $this->adapter->getTtl($key);
     }
 
+    /**
+     * @param string $key
+     *
+     * @return bool True if the key does exist, false if the key does not exist.
+     *
+     * @throws \InvalidArgumentException
+     */
     public function has($key)
     {
         $this->adapter->has($key);
     }
 
+    /**
+     * Remove the existing timeout on key, turning the key from volatile (a key with an expire set)
+     * to persistent (a key that will never expire as no timeout is associated).
+     *
+     * @param string $key
+     *
+     * @return bool True if the persist was success, false if the persis was unsuccessful.
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     */
     public function persist($key)
     {
         $this->adapter->persist($key);
diff --git a/src/Implementation/StringTrait.php b/src/Implementation/StringTrait.php
index 8a32175..4a9e984 100644
--- a/src/Implementation/StringTrait.php
+++ b/src/Implementation/StringTrait.php
@@ -1,47 +1,136 @@
 <?php namespace AdammBalogh\KeyValueStore\Implementation;
 
+use AdammBalogh\KeyValueStore\Exception\InternalException;
+use AdammBalogh\KeyValueStore\Exception\KeyAlreadyExistsException;
+use AdammBalogh\KeyValueStore\Exception\KeyNotFoundException;
+
 trait StringTrait
 {
+    use AdapterTrait;
+
+    /**
+     * @param string $key
+     * @param string $value
+     *
+     * @return int The length of the string after the append operation.
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
     public function append($key, $value)
     {
         $this->adapter->append($key, $value);
     }
 
-    public function decr($key)
+    /**
+     * @param string $key
+     *
+     * @return int The value of key after the decrement
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
+    public function decrement($key)
     {
-        $this->adapter->decr($key);
+        $this->adapter->decrement($key);
     }
 
-    public function decrBy($key, $decrement)
+    /**
+     * @param string $key
+     * @param int $decrement
+     *
+     * @return int The value of key after the decrement
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
+    public function decrementBy($key, $decrement)
     {
-        $this->adapter->decrBy($key, $decrement);
+        $this->adapter->decrementBy($key, $decrement);
     }
 
+    /**
+     * @param string $key
+     *
+     * @return string The value of the key
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
     public function get($key)
     {
         $this->adapter->get($key);
     }
 
+    /**
+     * @param string $key
+     *
+     * @return int
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
     public function getValueLength($key)
     {
         $this->adapter->getValueLength($key);
     }
 
-    public function incr($key)
+    /**
+     * @param string $key
+     *
+     * @return int The value of key after the increment
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
+    public function increment($key)
     {
-        $this->adapter->incr($key);
+        $this->adapter->increment($key);
     }
 
-    public function incrBy($key, $increment)
+    /**
+     * @param string $key
+     * @param int $increment
+     *
+     * @return int The value of key after the increment
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyNotFoundException
+     * @throws InternalException
+     */
+    public function incrementBy($key, $increment)
     {
-        $this->adapter->incrBy($key, $increment);
+        $this->adapter->incrementBy($key, $increment);
     }
 
+    /**
+     * @param string $key
+     * @param string $value
+     *
+     * @return bool True if the set was successful, false if it was unsuccessful
+     *
+     * @throws \InvalidArgumentException
+     */
     public function set($key, $value)
     {
         $this->adapter->set($key, $value);
     }
 
+    /**
+     * @param string $key
+     * @param string $value
+     *
+     * @return bool True if the set was successful, false if it was unsuccessful
+     *
+     * @throws \InvalidArgumentException
+     * @throws KeyAlreadyExistsException
+     */
     public function setIfNotExists($key, $value)
     {
         $this->adapter->setIfNotExists($key, $value);
diff --git a/src/KeyValueStore.php b/src/KeyValueStore.php
index 87cc8b7..58b43f3 100644
--- a/src/KeyValueStore.php
+++ b/src/KeyValueStore.php
@@ -2,10 +2,12 @@
 
 use AdammBalogh\KeyValueStore\Contract\AdapterInterface;
 use AdammBalogh\KeyValueStore\Implementation\AdapterTrait;
+use AdammBalogh\KeyValueStore\Implementation\KeyTrait;
+use AdammBalogh\KeyValueStore\Implementation\StringTrait;
 
 class KeyValueStore implements AdapterInterface
 {
-    use AdapterTrait;
+    use AdapterTrait, KeyTrait, StringTrait;
 
     /**
      * @param AdapterInterface $adapter